1. Field of the Invention
The present invention is generally in the field of electronics. More particularly, the present invention is in the field of electronic devices relying on battery power.
2. Background
An important feature of an electronic device, such as a cellular telephone, is the accurate determination of the charge remaining in the power source, such as a battery, powering the electronic device. The accurate determination of charge remaining in the power source is critical since such information is typically used by the electronic device to determine a course of action, such as to provide the user with an indication that the power source is low or to disable the electronic device completely by automatically turning it off.
To determine the charge remaining in a power source providing power to an electronic device, such as a battery providing power to a cellular telephone, a “power gauge circuit” (also referred to simply as a “power gauge” in the present application, and sometimes referred to as a “fuel gauge” or “gas gauge” in the industry) can be used to determine the total charge consumed from the power source, which can then be also used to determine the charge remaining in the power source. Such a power gauge circuit typically includes an analog to digital converter which samples a voltage corresponding to the current drawn from the power source by the electronic device. The analog to digital converter provides digital outputs to an accumulator which receives and maintains a sum of the digital outputs. The sum of digital outputs can then be used to determine the total charge consumed from the power source.
However, such a power gauge circuit can consume a substantial amount of power from the power source since, for example, the analog to digital converter and the accumulator in the conventional power gauge circuit must remain continuously on to measure the charges consumed from the power source. Moreover, since the current drawn from an electronic device can vary greatly during its various modes of operation, for example the current can vary from just 1.0 milliamps to over 100.0 milliamps, a very high resolution and complex analog to digital converter is typically required to operate over a very large range of values. Such high resolution analog to digital converters can also disadvantageously consume a substantial amount of power from the power source. Consequently, given the limited capacity of power sources, e.g. batteries, used in portable electronic devices, conventional power gauges present significant shortcomings and disadvantages.